Diffractive microstructure and a method of producing the same
Diffractive microstructure comprising micro-protrusions or microgrooves or a combination thereof and method of producing the same. The microstructure is formed in a layer of a thermoplastic carbohydrate polymer or a polymer derived from a carbohydrate material, said polymer having a glass transition point of less than 210° C. The thermoplastic polymer is preferably selected from the group of native starch, dextrin, native hemicellulose, native cellulose, poly(lactic acid), polylactides, polycaprolactone, starch derivatives, dextrin derivatives, hemicellulose derivatives, cellulose derivatives, and mixtures thereof. The invention provides an inexpensive and reliable way of incorporating into the products safety markings, which allow for visual inspection or detection, such as holograms and barcodes.
1. A diffractive microstructure consisting of micro-protrusions or microgrooves or a combination thereof formed in a layer,
wherein said layer consists of a thermoplastic carbohydrate polymer,
said polymer having a glass transition point of less than 210° C., wherein the thermoplastic carbohydrate polymer is a hydrophobic starch ester having a degree of substitution of at least 1.7, and wherein the thermoplastic carbohydrate polymer is plasticized with a hydroxyl compound selected from the group of C2 to C4 alcohols having 1-5 hydroxyl groups, sorbitol and mixtures thereof,
wherein said layer is a self-supporting layer or film having a thickness of from 0.1 to less than 12 micrometers.
2. The microstructure according to claim 1 , wherein the micro-protrusions or microgrooves or the combination thereof form a detectable pattern.
3. The microstructure according to claim 1 , which is capable of diffracting monochromatic or polychromatic light.
4. The microstructure according to claim 3 , which is capable of diffracting light in the visual range, in the ultraviolet range, in the infrared range or in a broad wave length range comprising visual, ultraviolet and/or infrared light.
5. The microstructure according to claim 1 , comprising a barcode tag or a safety marking or an identification label or a combination thereof.
6. The microstructure according to claim 1 , comprising a cinegram, an exelgram or a hologram.
7. The microstructure of claim 1 , wherein the thermoplastic carbohydrate polymer is a hydrophobic starch ester having a degree of substitution of at least 2.0.
8. The microstructure of claim 1 , wherein the thermoplastic carbohydrate polymer is plasticized with a glycerol or sorbitol or mixtures thereof.